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Cool story from the MAKE Flickr pool: Alex French designed and carefully machined a torsion-set engagement ring to propose to his longtime sweetheart, Colleen. He studied up, tooled up with a Sherline 4000A hobby lathe/mill/drill press combo, then turned, bored, and milled the ring before setting the stone, himself, all while working secretly in a spare bedroom in their shared home.

I turned to Machinery’s Handbook for structural analysis, based on looking at the tension setting as a single loop of a torsion spring…If I’m correct, 1 pound of force at the stone setting deforms the ring about 0.007 inches. The opening was milled to dimensions that creatae about 2 pounds of force on the ring. It would take about four pounds of force to open the ring enough for the stone to slide out radially, or less to slide out along the ring finger axis.

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and makezine.com. My work has also appeared in ReadyMade, c’t – Magazin für Computertechnik, and The Wall Street Journal.